Internal Implant-abutment Connections Research Articles

In vitro assessment of internal implant-abutment connections with different cone angles under static loading using synchrotron-based radiation

BackgroundThe stability of implant-abutment connection is crucial to minimize mechanical and biological complications. Therefore, an assessment of the microgap behavior and abutment displacement in different implant-abutment designs was performed.MethodsFour implant systems were tested, three with a conical implant-abutment connection based on friction fit and a cone angle < 12 ° (Medentika, Medentis, NobelActive) and a system with an angulated connection (< 40°) (Semados). In different static loading conditions (30 N − 90º, 100 N − 90º, 200 N − 30º) the microgap and abutment displacement was evaluated using synchrotron-based microtomography and phase-contrast radioscopy with numerical forward simulation of the optical Fresnel propagation yielding an accuracy down to 0.1 μm.ResultsMicrogaps were present in all implant systems prior to loading (0.15–9 μm). Values increased with mounting force and angle up to 40.5 μm at an off axis loading of 100 N in a 90° angle.ConclusionsIn contrast to the implant-abutment connection with a large cone angle (45°), the conical connections based on a friction fit (small cone angles with < 12°) demonstrated an abutment displacement which resulted in a deformation of the outer implant wall. The design of the implant-abutment connection seems to be crucial for the force distribution on the implant wall which might influence peri-implant bone stability.

Comparative Analysis of Microbial Leakage in Implant Recess of Three Different Internal Implant Abutment Connections: An In Vitro Study

Comparative Analysis of Microbial Leakage in Implant Recess of Three Different Internal Implant Abutment Connections: An In Vitro Study

Assessment of Microgap and Bacterial Leakage of Two Types of Internal Implant-Abutment Union.

The current research was done to assess microbial seepage of two types of internal implant-abutment connections. Twenty dental implants are categorized into two groups. Group A fixtures with an internal hexagonal geometry and group B fixtures with a tri-lobe internal connection. All implant-abutment assemblies underwent a three-week incubation period at 37°C in sterile tubes containing 5 mL of Staphylococcus aureus broth culture. Through the use of Gram stain and biochemical processes, the resultant colonies were recognized. The mean Log10 colony forming unit (CFU) in group A was 8.4 and in group B was 7.2. The variation between both groups was found to be considerable (P < 0.05). Microgap was more in group B compared to group A. Bacteria may infiltrate the small area between the implant and the abutment. Compared to dental implant fixtures with a tri-lobe internal connection, there was a noticeably higher Log10 CFU in dental implant fixtures with an internal hexagonal geometry.

Risk Indicators Affecting the Survival of the Mandibular First Molar Adjacent to an Implant at the Mandibular Second Molar Site: A Retrospective Study.

This study aimed to compare the survival of mandibular first molars (MnM1s) adjacent to implants placed in mandibular second molar sites (ImM2s) with MnM1s adjacent to mandibular second molars (MnM2s) and to investigate risk indicators affecting the survival of MnM1s adjacent to ImM2s. A total of 144 patients who had MnM1s adjacent to ImM2s and MnM1s adjacent to MnM2s on the contralateral side were included in this study. Clinical variables and radiographic bone levels were evaluated. The survival of MnM1s adjacent to ImM2s or MnM2s was evaluated using a Kaplan–Meier analysis and Cox proportional hazards model. The 5-year cumulative survival rates of MnM1s adjacent to ImM2s and MnM2s were 85% and 95%, respectively. MnM1s adjacent to ImM2s of the internal implant-abutment connection type had higher multivariate hazard ratios (HR) for loss. MnM1s that had antagonists with implant-supported prostheses also had higher HR for loss. The multivariate HR for the loss of MnM1s adjacent to ImM2s with peri-implant mucositis was 3.74 times higher than MnM1s adjacent to healthy ImM2s. This study demonstrated several risk indicators affecting the survival of MnM1s adjacent to ImM2s. It is suggested that supportive periodontal and peri-implant therapy combined with meticulous occlusal adjustment can prolong the survival of MnM1s and ImM2s.

SECONDARY ETIOLOGICAL FACTORS IN THE DEVELOPMENT OF PERI-IMPLANTITIS

Purpose: The aim of this review was to investigate the potential impact of secondary etiological factors on the development of peri-implant infections. Results: During the review process we found sufficient evidence to define the following factors as secondary etiological factors for the development of peri-implantitis: a history of periodontitis; implant surface characteristics; suprastructure characteristics; cemented restorations; implant-abutment connection; smoking; diabetes and peri-implant mucosa characteristics. Conclusion: To reduce the risk of peri-implantitis, the following recommendations should be considered: (1) in partially edentulous patients, implant treatment should start after elimination of the periodontal infection and after the establishment of a stable periodontal status; (2) implants should be placed in areas where there is a minimum of 2 mm of keratinized mucosa; (3) an internal implant-abutment connection and screw-retained suprastructures are preferred; (4) supra structures should be planned carefully to facilitate good oral hygiene; and (5) smoking cessation should be promoted and (6) only patients with controlled diabetes should undergo implant placement.

Internal Hexagon vs Conical Implant-Abutment Connections: Evaluation of 3-Year Postloading Outcomes.

Different types of internal implant-abutment connections, namely hexagon and conical, have been used for implant restoration. However, data regarding the benefits of these internal connections in terms of clinical outcomes are scarce. Accordingly, the aim of this study was to compare radiographic marginal bone loss (RMBL) and associated implant complications between implants with internal hexagon (IH) connections and those with internal conical (IC) connections. Forty-nine patients with 98 implants (2 per patient) placed in the posterior mandible were recruited. All implants were inserted in pairs into solid D2 bone according to a randomized sequence; the first patient received an IH connection implant on the mesial side, while the second patient received an IC connection implant on the mesial side. Each patient received 1 implant with an IH connection and 1 with an IC connection, placed side by side. Four months after placement, all implants were loaded with single screw-retained ceramic restorations with IH or IC connections. RMBL and complications, including implant/prosthesis failure, were recorded at the time of implant loading (baseline) and at 6, 12, and 36 months after loading. The results revealed no significant between-group differences in RMBL (P = .74), gingival bleeding on probing (P = .29), and complications (P = .32). Thus, the type of internal implant-abutment connection did not affect clinical outcomes, including RMBL and implant/prosthesis failure. Future studies should additionally evaluate long-term prosthesis-related complications, such as screw loosening and fracture, between the 2 types of internal connections.

Evaluation of Milled Titanium versus Laser Sintered Co-Cr Abutments on the Marginal Misfit in Internal Implant-Abutment Connection.

The precision of fit at the implant-abutment connection is an important criterion for the clinical success of restorations and implants. Several factors are involved among which are the abutment materials and manufacturing techniques. The aim of this study was to investigate the effect of two materials and methods of manufacturing implant abutments, milled titanium versus laser sintered Co-Cr, on the marginal misfit at the implant-abutment interface. Scanning electron microscopes (SEM) were used to geometrically measure the marginal vertical discrepancy of a total of 80 specimens, classified into eight categories, according to the implant system and abutment. The data were statistically analyzed by Student’s paired t test, one-way and two-way ANOVA with the Bonferroni-Holm correction at the significance level of p = 0.05. Milled titanium abutments demonstrated the lowest misfit values in the implant systems analyzed. The marginal fit of all the groups was within the clinically acceptable range for implant prostheses.

Clinical study on screw loosening in dental implant prostheses: a 6-year retrospective study.

ObjectivesIn this study, we determined the incidence and pattern of screw loosening in patients who received dental implants.Materials and MethodsPatients who received implants between January 2008 and October 2013 and completed their prosthetic rehabilitation were evaluated for the incidence, frequency, and onset of screw loosening using dental charts and radiographs. The association between each factor and screw loosening was analyzed using the chi-square test and a multivariate analysis with binary logistic regression models (P<0.05).ResultsTotal 1,928 implants were placed in 837 patients (448 males, 389 females), whose follow-up period after loading varied from 0.25 to 70 months (mean period, 31.5 months). Screw loosening occurred in 7.2% of implants. Most cases occurred less than six months after loading. Among those, 22.3% experienced recurrent screw loosening. Screw loosening was most common in the molar region (8.5%) and frequently associated with an implant diameter of ≥5 mm (14.2%). External implant–abutment connections (8.9%) and screw-retained implant prostheses (10.1%) showed higher incidence of problems than internal implant–abutment connections and cement-retained implants, respectively. Screw loosening was most common in implant prostheses with single crowns (14.0%).ConclusionWithin the limits of the current study, we conclude that the incidence of screw loosening differs significantly according to the position of implant placement, the type of implant and manufacturer, implant diameter, the type of implant–abutment connection, the type of retention in the implant prosthesis, and the type of implant prosthesis.

Clinical and patient-reported outcome of implant restorations with internal conical connection in daily dental practices: prospective observational multicenter trial with up to 7-year follow-up

BackgroundThe interpretation of the results of randomized clinical trials is often questioned in relation with daily circumstances in practices. This prospective observational multicenter study was instigated to reflect the need for information in real-life situations with dental implants with internal conical implant-abutment connection (Conelog implant system). The implants were followed up at least 5-year post-loading; survival analysis (Kaplan-Meier), changes of soft tissue, and bone level over time, as well as patient satisfaction were evaluated.ResultsIn total, 130 dental implants were placed in 94 patients (64 female, 30 male). Mean age of patients was 50.4 ± 13.7. At 5-year post-loading, 104 implants in 76 patients were available for evaluation. The cumulative implant survival rate was 96.6%. After an initial bone remodeling process post-surgery (bone loss of − 0.52 ± 0.55 mm), the bone level change remained clinically stable from loading to 5-year post-loading (− 0.09 ± 0.43 mm). Patient satisfaction surveyed by questionnaire (comfort, ability to chew and taste, esthetics, general satisfaction) steadily increased towards the end. At the last study follow-up, all the patients rated their general satisfaction as either very satisfied (87.5%) or satisfied (12.5%).ConclusionThe study implants have shown to be highly effective with reliable peri-implant tissue stability over the 5 to 7 years of observation for both single tooth restorations and fixed partial dentures while used in standard conditions in daily dental practice. The results obtained are comparable with those obtained in controlled clinical trials.

Comparison of stress distribution in a three unit cement retained implant supported prosthesis with different implant abutment connections: A photoelastic analysis

Aim: With the emphasis on success of implant supported prosthesis, and health of the surrounding tissues that are related to accuracy, and fit between the implant components, stability at implant abutment interface is of prime importance. The aim of this study is to evaluate and compare the stress distribution in three unit cement retained implant supported fixed partial denture with different implant abutment connections through photo elasticity. Materials and methods: Two photo elastic resin models were fabricated of standard dimensions (44mmx22mmx10mm). Group I sample: Three unit cement retained implant supported fixed partial denture with Internal implant abutment connection (Internal hexagonal connection) (Paltop Advanced, Keystone Dental Company, US)Group II sample: Three unit cement retained implant supported fixed partial denture with conical Morse taper connection (1.5 degree Morse taper) (Paltop Conical Active, Keystone Dental Company, US). Three unit cement retained implant supported fixed partial denture simulated missing mandibular first molar. Axial and oblique loads of 100N were placed on each implant and pontic area for 10 sec. Ten tests were done for each group. The stress values around the implants were derived from the colored fringe patterns obtained through polariscope, which were photographed after load applications from which values were derived. Results: Under axial loading, there was statistically significant difference between internal hexagonal connection and Morse taper connection in three unit implant supported prosthesis. Stresses were more in Group II sample with Morse taper connection. Under oblique loading, there was no statistically significant difference between Group I and Group II samples. Conclusion: Within the limitations of this in vitro study, it can be concluded that Internal hexagonal connection showed less stresses as compared to Morse taper connection in a three unit cement retained implant supported prosthesis. Stresses were concentrated more in apical area under axial loading; while under oblique loading stresses were seen on the side of application of force on the body of the implant and on the apical region. However, stresses were uniformly distributed in both groups I and group II samples. In both groups stresses under oblique loading were more than axial loading, but that was not statistically significant.

European Association for Osseointegration Delphi study on the trends in Implant Dentistry in Europe for the year 2030.

To assess the potential trends for the year 2030 in dental implant dentistry in Europe using the Delphi methodology. A steering committee and a management team of experts in implant dentistry were created and validated a questionnaire including 60 questions, divided in eight topics. The survey was conducted in two rounds using an anonymous questionnaire, which provided the participants in the second round with the results of the first. Each question had three possible answers, and the results were expressed as percentages. A total of 138 experts were invited to participate in the survey. From all the invited experts, 52 answered in both the first and second rounds. Three different consensus categories were established based on the percentage of agreement: no consensus (<65%); moderate consensus (65%-85%); and high consensus (≥86%). Within the topic categories, a consensus was reached (mainly moderate consensus) for the majority of questions discussed among experts during a face to face consensus meeting. However, consensus was not reached for a small number of questions/topics. About 82% of the questions reached consensus. The consensus points towards a lower number of implants to replace chewing units, with implants surfaces made of bioactive materials with reduced micro-roughness using mainly customized abutments with polished surfaces and an internal implant-abutment connection (85%). CBCT-3D technologies will be the main tool for pre-surgical implant placement diagnosis together with direct digital restorative workflows. There will be an increase in the incidence of peri-implantitis, although there will be more efficient interventions its treatment and prevention.

In vitro assessment of connection strength and stability of internal implant-abutment connections

BackgroundVarious connections have been machined to improve the fit between the dental abutment and implant. In vivo, the instability created by imprecisely fitting components can cause soft tissue irritation and bacterial colonization of the implant system. The aim of this study was to quantify abutment stability under in vitro force applications. MethodsAbutment stability and fit were quantitatively measured after application of rotational, vertical, and horizontal forces. FindingsThe abutment connection held by friction (Friction-Fit) was the only group to have 0° angular rotation. A significantly greater vertical force was required to pull the abutment from the implant for the Friction-Fit connection as compared to all other experimental groups. The abutment connection held by a mechanically locking friction-fit with four grooves (CrossFit) and Friction-Fit demonstrated significantly lower lateral movement as compared to all other connections. The remaining connections evaluated included two hexagon connections that rely on screw placement for abutment fit (Conical + Hex #1 and Conical + Hex #2), one connection with protruding slots to align with recessed channels inside the implant (Conical + 6 Indexing Slots), and an internal connection that allows for abutment indexing every 120° (Internal Tri-Channel). InterpretationInternal connection geometry influenced the degree of abutment movement. Friction-Fit and CrossFit connections exhibited the lowest rotational and horizontal motions. Significant differences were found between Friction-Fit and CrossFit following the application of a vertical force, with the Friction-Fit requiring a significantly greater pull force to separate the abutment from the implant.

A systematic review of the influence of the implant-abutment connection on the clinical outcomes of ceramic and metal implant abutments supporting fixed implant reconstructions.

The objective of this systematic review was to assess the influence of implant-abutment connection and abutment material on the outcome of implant-supported single crowns (SCs) and fixed dental prostheses (FDPs). An electronic Medline search complemented by manual searching was conducted to identify randomized controlled clinical trials, prospective and retrospective studies with a mean follow-up time of at least 3years. Patients had to have been examined clinically at the follow-up visit. Failure and complication rates were analyzed using robust Poisson regression, and comparisons were made with multivariable Poisson regression models. The search provided 1511 titles and 177 abstracts. Full-text analysis was performed for 147 articles resulting in 60 studies meeting the inclusion criteria. Meta-analysis of these studies indicated an estimated 5-year survival rate of 97.6% for SCs and 97.0% for FDPs supported by implants with internal implant-abutment connection and 95.7% for SCs and 95.8% for FDPs supported by implants with external connection. The 5-year abutment failure rate ranged from 0.7% to 2.8% for different connections with no differences between the types of connections. The total number of complications was similar between the two connections, yet, at external connections, abutment or occlusal screw loosening was more predominant. Ceramic abutments, both internally and externally connected, demonstrated a significantly higher incidence of abutment fractures compared with metal abutments. For implant-supported SCs, both metal and ceramic abutments with internal and external connections exhibited high survival rates. Moreover, implant-supported FDPs with metal abutments with internal and external connections for also showed high survival rates.

Very low certainty in evidence suggesting that internal implant-abutment connections result in negligible bone loss and similar survival and complication rates compared with external implant-abutment connections

Very low certainty in evidence suggesting that internal implant-abutment connections result in negligible bone loss and similar survival and complication rates compared with external implant-abutment connections

Clinical Comparison of Screw-Retained and Screwless Morse Taper Implant-Abutment Connections: One-year Postloading Results.

The purpose of this study was to clinically evaluate the screwless Morse taper implant-abutment connection type, in which the retention screw is totally eliminated, in terms of stability, success, periodontal parameters, and marginal bone levels after 1 year of function by comparing it with a passive fit internal implant-abutment connection, wherein a space exists between the matching components. Each edentulous subject received an implant with a screwless Morse taper connection (MT) in the left canine area of the mandible and an implant with a screw-retained implant-abutment connection (SR) in the right canine area of the mandible. All implants were loaded 6 weeks later. All cases were restored with a cemented bar-retained mandibular overdenture opposing a maxillary complete denture. Clinical recalls at 6 months and 12 months postloading were scheduled and the MT and SR implants were compared in terms of success, survival, primary and secondary implant stability, marginal bone loss, soft tissue response, and mechanical complications. The results were statistically analyzed. A total of 20 subjects were included (10 females, 10 males; average age: 61.60 years) and a total of 40 implants were inserted. No implant failure or technical problem was detected for either MT or SR implants. Marginal bone loss around MT and SR implants did not show any significant differences at 6 weeks after surgery (time of loading) or at 6 months or 12 months postloading (P > .05). Periodontal parameters such as gingival index and probing pocket depth of MT and SR implants likewise did not differ significantly at 6 months and 12 months postloading (P > .05). Primary stability values of MT and SR implants did not differ significantly when measured with the insertion torque device (mean of 68.10 Ncm for MT and 64.20 Ncm for SR implants; P = .564), nor when measured with the electronic percussive testing device (mean of -5.30 for the MT and -5.35 for the SR implants; P = .398). However, MT implants showed lower stability at the time of loading (6 weeks) and 6 months postloading (P = .037 and P = .003, respectively). Stability values did not show any significant differences 12 months postloading (P > .05). Within the limitations of this clinical study, it can be concluded that implants with screwless Morse taper and passive fit internal connections show comparable technical and biologic results after 1 year of function.

The effect of repeated torque tightening on total lengths of implant abutments in different internal implant‒abutment connections.

Background. Since the misfit of crown has an important role in clinical performance of implant-supported prostheses, and due to the impact of the settling effect on misfit, the aim of this study was to investigate the impact of torque forces on the total lengths of narrow and short implant abutments in different internal implant‒abutment connections. Methods. In four different implant‒abutment connections, 8 analog implants with a normal diameter (4 mm) and narrow abutment (4.5 mm) were selected from groups of internal hex, internal octagon, morse hex 6° and morse hex 11°. Each of them was mounted within plaster type IV, and 32 samples were obtained. Then, the amount of vertical displacement was measured by closing the impression copings and applying torques of 20 25 and 30 Ncm. This stage was repeated for the abutment. In the next stage, the resin pattern was built and measurements were performed after applying the torques mentioned. Finally, after making the frame, this stage was repeated, and the settling effect was statistically analyzed with ANOVA. Results. In the stages of impression coping, resin pattern and final prosthesis, HEXAGONE had significantly the highest and OCTAGONE had the lowest rates of settling, and the settling of morse hex 11° and 6° was between them. Conclusion. Octagon implant had significantly the lowest settling in various clinical and laboratory stages by applying different torques.

Stress and strain distribution in three different mini dental implant designs using in implant retained overdenture: a finite element analysis study.

Purpose of this study was to characterize and analyze stress and strain distribution occurring in bone and implants and to compare stress and strain of three different implant designs. Three different mini dental implant designs were included in this study: 1. a mini dental implant with an internal implant-abutment connection (MDIi); 2. a mini dental implant with an external implant-abutment connection (MDIe); 3. a single piece mini dental implant (MDIs). All implant designs were scanned using micro-CT scans. The imaging details of the implants were used to simulate models for FEA. An artificial bone volume of 9×9 mm in size was constructed and each implant was placed separately at the center of each bone model. All bone-implant models were simulatively loaded under an axial compressive force of 100 N and a 45-degree force of 100 N loading at the top of the implants using computer software to evaluate stress and strain distribution. There was no difference in stress or strain between the three implant designs. The stress and strain occurring in all three mini dental implant designs were mainly localized at the cortical bone around the bone-implant interface. Oblique 45° loading caused increased deformation, magnitude and distribution of stress and strain in all implant models. Within the limits of this study, the average stress and strain in bone and implant models with MDIi were similar to those with MDIe and MDIs. The oblique 45° load played an important role in dramatically increased average stress and strain in all bone-implant models. Mini dental implants with external or internal connections have similar stress distribution to single piece mini dental implants. In clinical situations, the three types of mini dental implant should exhibit the same behavior to chewing force.

Effect of the Coronal Wall Thickness of Dental Implants on the Screw Joint Stability in the Internal Implant-Abutment Connection.

To evaluate the effect of implant coronal wall thickness on load-bearing capacity and screw joint stability. Experimental implants were customized after investigation of the thinnest coronal wall thickness of commercially available implant systems with a regular platform diameter. Implants with four coronal wall thicknesses (0.2, 0.3, 0.4, and 0.5 mm) were fabricated. Three sets of tests were performed. The first set was a failure test to evaluate load-bearing capacity and elastic limit. The second and third sets were cyclic and static loading tests. After abutment screw tightening of each implant, vertical cyclic loading of 250 N or static loading from 250 to 800 N was applied. Coronal diameter expansion, axial displacement, and removal torque values of the implants were compared. Repeated measures analysis of variance (ANOVA) was used for statistical analysis (α = .05). Implants with 0.2-mm coronal wall thickness demonstrated significantly low load-bearing capacity and elastic limit (both P < .05). These implants also showed significantly large coronal diameter expansion and axial displacement after screw tightening (both P < .05). Greater vertical load and thinner coronal wall thickness significantly increased coronal diameter expansion of the implant, axial displacement of the abutment, and removal torque loss of the abutment screw (all P < .05). Implant coronal wall thickness of 0.2 mm produces significantly inferior load-bearing capacity and screw joint stability.

Three-Dimensional Finite Element Analysis of the Stress Distribution at the Internal Implant-Abutment Connection.

This study investigated stress distribution in four different implant-abutment interface conditions in the internal tapered connection implant system. Four different implant diameters (3.5 mm, 4.0 mm, 4.5 mm, and 5.0 mm) and two abutment types (hexagonal and conical) were simulated. Four unique implant-abutment interface conditions were assumed based on wall thickness, mating surface length, distance to the vertical stop, and abutment shape. Axial and oblique loading was applied during abutment screw preload, and the Von Mises stresses were measured at the implant-abutment and abutment-screw interfaces. The implant-abutment interface stress decreased as the wall thickness increased. As the mating surface increased, the stress distribution trended downward, and when the distance to the implant vertical stop was 0 μm, the Von Mises stress was extremely high at the vertical stop. Despite their different shapes, the abutments showed similar stress distributions. However, the maximum Von Mises stress was higher in the conical connection than in the hexagonal connection, particularly at the contralateral side to loading. To decrease the stress distribution at the implant-abutment interface, the implant wall thickness, mating surface contact length, distance to the vertical stop, and abutment shape should be carefully considered.

Axial displacement of external and internal implant-abutment connection evaluated by linear mixed model analysis.

To analyze the axial displacement of external and internal implant-abutment connection after cyclic loading. Three groups of external abutments (Ext group), an internal tapered one-piece-type abutment (Int-1 group), and an internal tapered two-piece-type abutment (Int-2 group) were prepared. Cyclic loading was applied to implant-abutment assemblies at 150 N with a frequency of 3 Hz. The amount of axial displacement, the Periotest values (PTVs), and the removal torque values(RTVs) were measured. Both a repeated measures analysis of variance and pattern analysis based on the linear mixed model were used for statistical analysis. Scanning electron microscopy (SEM) was used to evaluate the surface of the implant-abutment connection. The mean axial displacements after 1,000,000 cycles were 0.6 μm in the Ext group, 3.7 μm in the Int-1 group, and 9.0 μm in the Int-2 group. Pattern analysis revealed a breakpoint at 171 cycles. The Ext group showed no declining pattern, and the Int-1 group showed no declining pattern after the breakpoint (171 cycles). However, the Int-2 group experienced continuous axial displacement. After cyclic loading, the PTV decreased in the Int-2 group, and the RTV decreased in all groups. SEM imaging revealed surface wear in all groups. Axial displacement and surface wear occurred in all groups. The PTVs remained stable, but the RTVs decreased after cyclic loading. Based on linear mixed model analysis, the Ext and Int-1 groups' axial displacements plateaued after little cyclic loading. The Int-2 group's rate of axial displacement slowed after 100,000 cycles.